Pad printing is a method of marking ophthalmic lenses. This method can involve subjecting the face of a lens to be marked to a corona discharge, a flame, or ionized air in order to increase the surface energy and thereby improve adherence of the surface to be marked. The lens can then be marked with a marking using pad transfer or silk screening printing with a special marking ink. The ink is then dried. Thereafter, the ink component can be removed with an appropriate solvent, if desired.
Pad printing methods can present difficulties to consistently and accurately position a lens with respect to a frame when placing a marking, such as a stamp or engraving, in a desired location on a lens, particularly a tinted or polarized lens.